Patent GB-829167-A (GB)
Title: Improvements in or relating to machines for grinding the points of twist drills
IPC: B24B3/24
Filed: 1958-04-22
Abstract: 829,167. Sharpening twist drills. GUHRING, O., GUHRING, A., and GUHRING, M., [trading as GOTTLIEB GUHRING.]. April 22, 1958 [May 6, 1957], No. 12774/58. Class 60. A machine for grinding the points of twist drills comprises a drill carrier 10 having an upper portion 12 arcuately adjustable on a lower portion 11, a member 18 on the upper portion for supporting the rear end of the drill and adjustable only in the direction of the drill axis, and a V-block 21 which is mounted on the upper portion for supporting the front end of the drill and is adjustable in accordance with the diameter of the drill so that, irrespective of the diameter of the drill, the axis of the drill always has the same position relative to the upper portion ; the lower portion 11 is pivotable on a pin 9 which is angularly adjustable relative to the operative surface 49 of a grinding wheel 48 on a pin 7 parallel to the surface 49 and mounted on a verticallyadjustable support 6. The upper portion 12 of the carrier has, at its rear end, a slot 13 along which can be adjusted a holder 14 having a threaded spindle 16 provided at one end with a knob 17 and at the other end with the member 18 which is shaped to support the rear end of a drill to be sharpened. The front end of the portion 11 carries a member 20 which is vertically adjustable in a guide 19 by rotation of a spiral-shaped disc 22 mounted on the member and co-operating with an abutment 24 on the portion 11, and has at its lower end the V-block 21 for supporting the front end of the drill. The drill is clamped in the V-block by one of three projections 31 which are mounted on a disc 30 and selected to suit the size of groove in the drill, the disc being carried on an arm 29 pivoted on a pin 27 in the portion 12 and connected to a handle 28 ; a spring 32 urges the selected projection into engagement with the drill. The upper portion is arcuately adjustable on a guide 34 on the lower portion 11 and can be clamped in a position determined by a scale 41 and index mark 42 by screws 37, 38. The centre of the arc of movement of the upper portion coincides with the point of intersection between the drill axis and the axis of rotation of the carrier about the pin 9 which is secured to a bearing 8 rotatable on the pin 7 and clampable in an angular position determined by a scale 44 and pointer 43 ; the two adjustments determine the angle at which the point of the drill is to be ground and may be within the range of 60 degrees to 140 degrees. The lower portion 11  is in two parts which can be moved relatively to each other in a direction parallel to the axis of the pin 7 by a screw 81 to enable the carrier to be set for sharpening drills having a right or left-hand twist. The pin 7 is carried on the support 6 which is vertically reciprocable to move the drill back and forth across the grinding wheel to ensure even wear of the surface 49 by a motor and worm drive 63 connected by bevel gearing 61, 62 to a spindle 60 screw-threaded into a sleeve 59 secured to the support 6 ; the motor is reversed at the end of each stroke by adjustable cams 66, 67 co-operating with limit switches 64, 65. The support can be manually adjusted by movement of a handle 72 which displaces a slide 68 carrying the motor 63 to disconnect the gears 61, 62 and by engaging a handle 77 through a coupling 78, which is normally spring-urged apart, with a gear 73 meshing with the gear 61. In operation, the carrier is set by means of the scales 41, 44 to a position corresponding to the angle of the cone to be ground on the drill and adjusted by the screw 81 for a right or left-hand twist. The grinding wheel is initially set to one of three positions which corresponds with the maximum size of drill in one of three ranges in drill diameters from, say, 1 to 10 m.ms., 10 to 20 m.ms. and 20 to 30 m.ms. by setting the disc 22 to position the V-block to its maximum position, moving a plate 26 on either the member 20 or block to its foremost position, as shown, and moving the grinding head 46 with the wheel 48 and its motor 47 by a handwheel 50 connected by gears 52 with a rack 53 so that the wheel is displaced axially to a position in which its surface 49 is 1 m.m. from the plate 26. The latter adjustments position the wheel for the maximum size of drill in the selected range a basic distance x from the point of intersection between the axes of the pin 9 and drill. A pointer on the wheel head is then brought into coincidence with a mark, corresponding to the maximum drill size in the range selected, on a scale secured to the machine and the plate 26 returned to its rear position. The grinding wheel can thereafter be set to any basic distance from the carrier for a drill within the selected range by adjustment of the wheel head by means of the handwheel 50 and scale, and the diameter of the drill accommodated by adjustment of the V-block 21 by means of the spiral-shaped disc 22. The drill is then sharpened by rocking the carrier to and fro on the pin 9. Coolant may be supplied to the wheel through pipes from a pump 4 and tank 3 in the lower part of the machine.